Rationale: Up to 50% of asthmatic patients have chronic or recurrent sinus disease. It is commonly claimed that sinusitis causes worsening of asthmatic symptoms, but that belief has never been subjected to rigorous evaluation. Hypothesis: Treatment of acute or subacute sinusitis improves subjective and objective markers of asthma. Subjects: Asthmatic children with CT evidence of sinusitis are the subjects of the study. Methods: Participants are evaluated with a symptom questionnaire, spirometry, plethysmography, methacholine challenge and analysis of nasal washings and sputum. They then receive either an antibiotic or placebo in a double-blind manner. The subjects continue on their usual regular asthma medications. After 3-4 weeks, they are re-evaluated to evaluate persisting sinus disease as well as any changes in asthma measures.